Nanooptics and photonics 
Optical characterization of Al2O3-YAG based eutectics: effect of plates thickness
D.O. Komarenko1, Yu.V. Siryk2, S.G. Ilchenko1, V.V. Multian1, O.M. Vovk2,
S.V. Nizhankovskyi2, V.Ya. Gayvoronsky1
1 Advanced Materials Nonlinear Optical Diagnostics Lab., Institute of Physics NAS of Ukraine, Prospect Nauky 46, 03028, Kyiv, Ukraine
E-mail: vlad@iop.kiev.ua
2 Institute for Single Crystals, National Academy of Sciences of Ukraine, Nauky Ave. 60, Kharkiv, Ukraine
Eutectics Al2O3-YAG and Al2O3-YAG:Ce are crystalline materials in which phases of the YAG garnet and Al2O3 sapphire penetrate each other, being formed during simultaneous growth. These eutectic crystals are characterized by a complex morphology, the so-called "china script" in which it is difficult to determine between phase intervals with different refractive indices. High dispersivity of the material increases path of the incident light beam and the efficiency of its capture by active cerium ions. The light emanating from a crystal after its irradiation consists of two components: the primary beam (usually 450 nm) and the beam obtained as a result of absorption and emission on active Ce3+ ions. Superposition of the scattered primary radiation with the emitted one is perceived by the human eye as white light. Both spectral components have different scattering mechanisms.
We have investigated efficiency of the elastic optical scattering and photoinduced extinction [1] of the pulsed laser radiation in Al2O3-YAG:Ce (0.25% wt. Ce) plates with optically quality polished interfaces against their thickness (0.5 – 2 mm) in visible and near IR ranges . It was obtained nonmonotonic dependence – 1 mm plate demonstrated the highest total transmittance decrease of the laser beam at 1064 nm among others. Magnitude of the reduction is crucially depends of the laser beam radius and its wavefront curvature. 
Meanwhile angular resoluted elastic optical scattering analysis at 532 nm revealed a minimal spreading of the transmitted light (67 deg, FWHM) in 1 mm Al2O3-YAG:Ce plate in comparison with 86-94 degs for the rest ones.
Obtained results can be applied for the light convertors based on Al2O3-YAG:Ce eutectics optimization.

1. V.Ya.Gayvoronsky, A.S.Popov et al. The Effect of Sintering Temperature on Linear and Nonlinear Optical Properties of YAG Nanoceramics. Springer Proc. in Phys. Springer, –2015.- 156.- 147.